A Distance Determination to the Small Magellanic Cloud with an Accuracy of Better than Two Percent Based on Late-type Eclipsing Binary Stars
Dariusz Graczyk, Grzegorz Pietrzyński, Ian B. Thompson, Wolfgang Gieren, Bartłomiej Zgirski, Sandro Villanova, Marek Górski, Piotr Wielgórski, Paulina Karczmarek, Weronika Narloch, Bogumił Pilecki, Monica Taormina, Radosław Smolec, Ksenia Suchomska, Alexandre Gallenne, Nicolas Nardetto, Jesper Storm, Rolf-Peter Kudritzki, Mikołaj Kałuszyński, Wojciech Pych
Abstract
Abstract We present a new study of late-type eclipsing binary stars in the Small Magellanic Cloud (SMC) undertaken with the aim of improving the distance determination to this important galaxy. A sample of 10 new detached, double-lined eclipsing binaries identified from the OGLE variable star catalogs and consisting of F- and G-type giant components has been analyzed. The absolute physical parameters of the individual components have been measured with a typical accuracy of better than 3%. All but one of the systems consist of young and intermediate population stars with masses in the range of 1.4 to 3.8 M ☉ . This new sample has been combined with five SMC eclipsing binaries previously published by our team. Distances to the binary systems were calculated using a surface brightness—color calibration. The targets form an elongated structure, highly inclined to the plane of the sky. The distance difference between the nearest and most-distant system amounts to 10 kpc with the line-of-sight depth reaching 7 kpc. We find tentative evidence of the existence of a spherical stellar substructure (core) in the SMC coinciding with its stellar center, containing about 40% of the young and intermediate age stars in the galaxy. The radial extension of this substructure is ∼1.5 kpc. We derive a distance to the SMC center of D SMC = 62.44 ± 0.47 (stat.) ± 0.81 (syst.) kpc corresponding to a distance modulus ( m − M ) SMC = 18.977 ± 0.016 ± 0.028 mag, representing an accuracy of better than 2%.